The present invention pertains to a gearshift lever for use with an automatic transmission in a motor vehicle and more particularly to a gearshift lever with a knob arranged at the top end of the gearshift lever, with a locking bar guided axially on the gearshift lever, and with a manually movable mechanism for actuating the locking bar relative to the gearshift lever.
Gearshift levers with a locking bar, which is designed as a tie rod that is guided axially movably in a gearshift lever, so that the locking bar must be pulled by manually actuating the locking knob, are known. For example, DE 25 30 784 A1 discloses a shifting device, in which a button, which is arranged on the underside of the handle grip of the gearshift lever and is pivotably movable in the engaged position, is used as an actuating means, which engages an opening of the locking bar via a coupling element. By actuating the button, it is pivoted into the handle grip as a result of which the locking bar is raised via the coupling member in the hollow gearshift lever.
DE 43 42 460 A1 discloses a gearshift lever assembly unit, which has a tubular lever component, at the top end of which a grip part is provided, which has a control knob, which is arranged rotatably in a hollow space of the grip part. This control knob cooperates with a spring-loaded actuating bar, which pretensions the control knob in the upward direction. The control knob must be moved by a human operator in the axial direction against the spring force to the extent that a locking means will lock the control knob in a defined position. The gearshift operations of the transmission of the motor vehicle now become possible. The actuating rod is designed as a push bar in such a design.
Furthermore, a shifting device for a motor vehicle transmission, whose actuating rod is designed as a push rod, has been known from EP 0 625 656 A1. A knob, whose axial extension is provided with an oblique surface at the end, is located in the grip piece, which is arranged at the top end of a hollow gearshift lever. If the knob is moved in the axial direction into the grip piece, the end-side oblique surface acts against a complementary oblique surface at the top end of the actuating rod. The actuating rod is thus guided downward in the axial direction until a locking mechanism holds it in the desired position, so that the shifting operations on the transmission become possible.
Furthermore, DE 195 13 809 C1, which forms the preamble, discloses a gearshift lever, which has a knob arranged at the top end of the gearshift lever, a locking bar guided axially on the gearshift lever, and means moved manually for actuating the locking bar relative to the gearshift lever, in which two of the means have teeth engaging one another and these means are arranged such that the movement of one of the means closer to the locking bar causes an axial movement of the locking bar. One essential drawback of this state of the art is that the initial forces needed to actuate the locking bar are relatively high during the actuation of the locking bar, so that very strong forces have to be applied with the thumb at the beginning to actuate the shifting device. This creates the feeling of a jerky shifting, whose force curve is unphysiological. The manufacture of such a shifting device is also relatively expensive.
The object of the present invention is to propose another gearshift lever for an automatic transmission of a motor vehicle, which avoids the above-mentioned drawback of the state of the art and has an improved power ratio during the actuation of the locking device of the gearshift lever.
Correspondingly, the gearshift lever for an automatic transmission in a motor vehicle with a knob arranged at the top end of the gearshift lever, with a locking bar guided axially at the gearshift lever, and with manually movable means for actuating the locking bar relative to the gearshift lever, in which two of the means have teeth engaging one another and these means are arranged such that a movement of at least one of the means toward the locking bar causes an axial movement of the locking bar, is improved to ensure that at least one of the two toothed segments extends along a curve, wherein the effective power ratio through a first of two curve radii is greater than the power ratio of the second radius.
It is achieved with the gearshift lever according to the present invention that the forces needed to actuate the locking bar are weak at the beginning and assume a higher value during the further course of the movement.
In a variant, at least one of the toothed segments may extend on an elliptical section (quadrant of an ellipse). This causes the power ratio to decrease continuously.
According to a specific embodiment of the present invention, the means for actuating the locking bar have a pushbutton with teeth on the inside, i.e., on the side directed toward the locking bar, wherein the said pushbotton is movable at right angles to the axis of the locking bar. Furthermore, the means for moving the locking bar may have a toothed segment, which is pivotably connected to the locking bar at one end and has, at least at the other end, an elliptical segment with teeth, which teeth engage linearly extending teeth of the pushbutton and lead to a raising of the locking bar during a linear movement of the pushbutton. In interaction with the elliptical segment-like shape of the teeth of the toothed segment, which toothed segment is pivotably connected to the locking bar on one side, the teeth of the pushbutton, which are linear, on the one hand, cause an optimal curve of the force ratio between the linear movement of the pushbutton and the locking bar, which leads to a pleasant, freely moving actuation of the locking bar. The forces to be applied for the actuation of the pushbutton and consequently of the locking bar are very weak at the beginning because of the favorable power ratio and they continuously increase as the movement progresses. This leads to a biomechanically pleasant actuation of the locking device connected to the locking bar.
It is obvious that the above-mentioned features of the present invention, which will be explained later, can be used not only in the particular combination described, but also in other combinations or alone, without going beyond the scope of the present invention.
Other features and advantages of the present invention will appear from the following description of a preferred exemplary embodiment with reference to the drawings.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.